T-cell engager antibodies enable T cells to control HBV infection and to target HBsAg-positive hepatoma in mice.

BACKGROUND & AIMS: Current antiviral therapies control but rarely eliminate HBV, leaving chronic HBV carriers at risk of developing hepatocellular carcinoma (HCC). Lacking or dysfunctional virus-specific adaptive immunity prevents control of HBV and allows the virus to persist. Restoring antiviral T-cell immunity could lead to HBV elimination and cure of chronically infected patients. METHODS: We constructed bispecific T-cell engager antibodies that are designed to induce antiviral immunity through simultaneous binding of HBV envelope proteins (HBVenv) on infected hepatocytes and CD3 or CD28 on T cells. T-cell engager antibodies were employed in co-cultures with healthy donor lymphocytes and HBV-infected target cells. Activation of the T-cell response was determined by detection of pro-inflammatory cytokines, effector function (by cytotoxicity) and antiviral effects. To study in vivo efficacy, immune-deficient mice were transplanted with HBVenv-positive and -negative hepatoma cells. RESULTS: The 2 T-cell engager antibodies synergistically activated T cells to become polyfunctional effectors that in turn elicited potent antiviral effects by killing infected cells and in addition controlled HBV via non-cytolytic, cytokine-mediated antiviral mechanisms. In vivo in mice, the antibodies attracted T cells specifically to the tumors expressing HBVenv resulting in T-cell activation, tumor infiltration and reduction of tumor burden. CONCLUSION: This study demonstrates that the administration of HBVenv-targeting T-cell engager antibodies facilitates a robust T-cell redirection towards HBV-positive target cells and provides a feasible and promising approach for the treatment of chronic viral hepatitis and HBV-associated HCC. LAY SUMMARY: T-cell engager antibodies are an interesting, novel therapeutic tool to restore immunity in patients with chronic hepatitis B. As bispecific antibodies, they bind envelope proteins on the surface of the hepatitis B virus (HBV) and CD3 or CD28 on T cells. This way, they induce a potent antiviral and cytotoxic T-cell response that leads to the elimination of HBV-positive cells. These bispecific T-cell engager antibodies are exciting therapeutic candidates for chronic hepatitis B and HBV-associated hepatocellular carcinoma.

A novel therapeutic hepatitis B vaccine induces cellular and humoral immune responses and breaks tolerance in hepatitis B virus (HBV) transgenic mice.

Therapeutic vaccines are currently being developed for chronic hepatitis B and C. As an alternative to long-term antiviral treatment or to support only partially effective therapy, they should activate the patient's immune system effectively to fight and finally control the virus. A paradigm of therapeutic vaccination is the potent induction of T-cell responses against key viral antigens - besides activation of a humoral immune response. We have evaluated the potential of a novel vaccine formulation comprising particulate hepatitis B surface (HBsAg) and core antigen (HBcAg), and the saponin-based ISCOMATRIX™ adjuvant for its ability to stimulate T and B cell responses in C57BL/6 mice and its ability to break tolerance in syngeneic HBV transgenic (HBVtg) mice. In C57BL/6 mice, the vaccine induced multifunctional HBsAg- and HBcAg-specific CD8+ T cells detected by staining for IFNγ, TNFα and IL-2, as well as high antibody titers against both antigens. Vaccination of HBVtg animals induced potent HBsAg- and HBcAg-specific CD8+ T-cell responses in spleens and HBcAg-specific CD8+ T-cell responses in livers as well as anti-HBs seroconversion two weeks post injection. Vaccination further reduced HBcAg expression in livers of HBVtg mice without causing liver damage. In summary, this study demonstrates therapeutic efficacy of a novel vaccine formulation in a mouse model of immunotolerant, chronic HBV infection.

Immune tolerance against HBV can be overcome in HBV transgenic mice by immunization with dendritic cells pulsed by HBVsvp.

In chronic Hepatitis B Virus (HBV) infection the function of dendritic cells (DC), T- and B-cells is impaired. DC vaccination is an option to overcome this. DC pulsed in vitro with HBV sub viral particles (HBVsvp) and used to immunize mice can activate HBV directed humoral and cellular immune responses. In the present study we vaccinated HBV transgenic mice as a model for chronic HBV infection and observed humoral and cellular immune responses. In these mice, the lacking immune response against HBV is mainly due to peripheral tolerance. HBVsvp, together with LPS as a co-activating molecule, were used for pulsing and in vitro activation of DC. HBV transgenic mice were injected with pulsed DC two times. Four weeks after DC vaccination humoral and cellular immune responses, viral antigen levels and liver histology were analyzed. DC vaccinated HBV-transgenic mice developed a strong HBV specific antibody and T-cell response after DC vaccination. Neither circulating HBV antigen levels nor viremia, however, were controlled. No liver damage was observed. These results demonstrate that in vitro activation of DC and loading with HBVsvp can overcome tolerance against HBV and reactivate B- and T-cell responses in HBV transgenic mice, but were not sufficient to lead to virus control in these mice. Vaccination using DC, the key players of cellular and humoral immunity, after in vitro reactivation promises to break tolerance against HBV and may help patients with chronic hepatitis B to clear the infection.

Not interferon, but interleukin-6 controls early gene expression in hepatitis B virus infection.

UNLABELLED: With about 350 million virus carriers, hepatitis B virus (HBV) infection remains a major health problem. HBV is a noncytopathic virus causing persistent infection, but it is still unknown whether host recognition of HBV may activate an innate immune response. We describe that upon infection of primary human liver cells, HBV is recognized by nonparenchymal cells of the liver, mainly by liver macrophages (Kupffer cells), although they are not infected. Within 3 hours, this recognition leads to the activation of nuclear factor kappa B (NF-kappaB) and subsequently to the release of interleukin-6 (IL-6) and other proinflammatory cytokines (IL-8, TNF-alpha, IL-1beta), but does not induce an interferon response. The activation of proinflammatory cytokines, however, is transient, and even inhibits responsiveness toward a subsequent challenge. IL-6 released by Kupffer cells after activation of NF-kappaB controls HBV gene expression and replication in hepatocytes at the level of transcription shortly after infection. Upon binding to its receptor complex, IL-6 activates the mitogen-activated protein kinases exogenous signal-regulated kinase 1/2, and c-jun N-terminal kinase, which inhibit expression of hepatocyte nuclear factor (HNF) 1alpha and HNF 4alpha, two transcription factors essential for HBV gene expression and replication. CONCLUSION: Our results demonstrate recognition of HBV patterns by nonparenchymal liver cells, which results in IL-6-mediated control of HBV infection at the transcriptional level. Thus, IL-6 ensures early control of the virus, limiting activation of the adaptive immune response and preventing death of the HBV-infected hepatocyte. This pattern recognition may be essential for a virus, which infects a new host with only a few virions. Our data also indicate that therapeutic neutralization of IL-6 for treatment of certain diseases may represent a risk if the patient is HBV-infected.